Details

Every instance of ff in the HTML version (but not the PDF version) is substituted by the character ﬀ. For example: "This option shows RAM buﬀer size", "The Sleep Timer powers oﬀ your player" and "It allows rapid access to the SHUﬄE and REPEAT modes". All of these appear at the end of chapter 5 (I noticed this in the e200 manual)

I think this is a problem due to Latex use of ligatures that isn't handled well by the HTML converter. I didn't notice this before so I don't know what changed to start causing this. I originally thought it was due to the recent use of \caps, but it also occurs for lower case instances of ff too.

A bit more investigation. I think my hunch is correct since Tex4ht converts the compiled DVI into HTML instead of parsing the .tex source files. Latex converts several character combinations in the source into a single character ligature, such as ff --> ﬀ. These are all treated fine by pdflatex. The ligatures are in the PDF and render just fine. The default behavior seems to be to revert ligatures and display individual characters. Tex4ht does this in most of the cases such as identified. However, it doesn't do this for the ligatures involving ff:

ff -->ﬀ (eﬀect)
ffi -->ﬃ (suﬃcient)
ffl --> ﬄ (Shuﬄe)

In fact, the situation is even worse in that it introduces a ligature that's absent from the PDF version of the document -- namely, in the case of SHUﬄE.